Electronic Supplementary Information

For

The anion-sensing polyanion: a molecular cobalt van adium oxide as multi-anion

sensor

Andrey Seliverstov,a,b Johannes Forster,a,b Magdalena Heiland,a Johannes Unfried,,b

Carsten Streba,b*

aInstitute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany

b previous address:Department Chemistry and Pharmacy, Inorganic Chemistry II, Friedrich-

Alexander-University Erlangen-Nuremberg, Egerlandstr. 1, 91058 Erlangen, Germany.

*Email: carsten.streb@uni-ulm.de, web: www.strebgroup.net

1. Instrumentation X-ray diffraction: Single-crystal X-ray diffraction studies were performed on a Nonius

Kappa CCD Single-crystal X-ray diffractometer equipped with a graphite monochromator

using MoKα radiation (wavelength λ(MoKα) = 0.71073 Å).

FT-IR spectroscopy: FT-IR spectroscopy was performed on a Shimadzu FT-IR-8400S

spectrometer. Samples were prepared as KBr pellets. Signals are given as

wavenumbers in cm-1 using the following abbreviations: vs = very strong, s = strong, m =

medium, w = weak and b = broad.

UV-Vis spectroscopy: UV-Vis spectroscopy was performed on a Shimadzu UV-

2401PC spectrophotometer, Varian Cary 50 spectrophotometer or Varian Cary 5G

spectrophotometer equipped with a Peltier thermostat. All systems were used with

standard cuvettes (d = 10.0 mm).

Thermogravimetry analysis (TGA): TGA was performed on a Setaram Setsys CS Evo,

30 - 900°C at 10K/min, 50 mL/min air, Graphite crucible 0.5 mL.

Elemental analysis: Elemental analysis was performed on a Euro Vector Euro EA 3000

Elemental Analyzer.

Atomic absorption spectroscopy: Atomic absorption spectroscopy analysis was

performed on a Perkin Elmer 5100 PC spectrometer.

Electronic Supplementary Material (ESI) for ChemComm.This journal is © The Royal Society of Chemistry 2014

Nuclear Magnetic Resonance Spectroscopy (NMR): 1H-NMR spectra were recorded

at 269.7 MHz on a JNM-EX270 FT NMR spectrometer (JEOL). The solvent was DMSO-

d6, data is given as chemical shifts δ in ppm.

Electrospray ionization mass spectrometry (ESI-MS) : ESI-MS measurements were

performed on an ultra-high resolution time-of-flight (UHR-TOF) Bruker Daltonik maXis,

an ESI-TOF-MS. Detection was in negative-ion mode and the source voltage was 4 kV.

The flow rates were 500 µL/hour. The drying gas (N2) was held at 180 °C. The machine

was calibrated prior to every experiment by direct infusion of the Agilent ESI-TOF low

concentration tuning mixture.

General remarks : All chemicals were purchased from Sigma Aldrich or ACROS and

were of reagent grade. The chemicals were used without further purification unless

stated otherwise. (n-Bu4N)4[V4O12] × 4H2O was synthesized as reported in the

literature.S1

2. Synthetic section: Synthesis of compound 1 Method 1:

(n-Bu4N)4[V4O12] (200 mg, 146.5 mmol) was dissolved in DMF (2 mL) and added to a

solution of Co(AcO)2·4H2O (18.2 mg, 73.1 mmol) in DMF (4 mL). Upon mixing, a

spontaneous colour change from pink to emerald green was observed. The clear, green

solution was stirred at room temperature for 2 h. The product was obtained a single

crystalline material by diffusion of diethyl ether or ethyl acetate into the mother liquor.

Yield: 65 mg (52.4 mmol, 71.4 % based on Co). Elemental analysis in wt.-% for

C50H111N3O14V4Co (calculated values in brackets): C 48.63 (48.39), H 9.25 (9.01), N 3.47

(3.39), V 16.58 (16.41), Co 4.48 (4.75). Characteristic IR-bands (in cm-1): 2959 (m), 2874

(vs), 1474 (s), 1379 (m), 1167 (s), 1109 (vs), 1057 (m), 1030 (s), 941 (m), 821 (b), 750

(m), 648 (b).

Method 2:

(n-Bu4N)4[V4O12] (200 mg, 146.5 mmol) was dissolved in DMF or MeCN (2 mL). The

resulting solution was added to a solution of Co(NO3)2·6H2O (21.3 mg, 73.0 mmol) in

DMF or MeCN (4 mL), which resulted in a spontaneous colour change of the reaction

mixture to dark green. After stirring at 60 °C overnight the mixture was allowed to cool to

RT. The product was obtained as emerald green crystals by diffusion crystallization

using EtAcO as diffusion solvent. Lower yields (ca. 30 %) were observed as ethyl

acetate decomposition (to give the required acetate ions) seems to be the limiting factor.

Figure S1: IR spectrum of compound 1.

Figure S2: UV-Vis spectrum of {CoV 4} in DMF: λmax1 = 724 nm, ε = 242.7 M-1 cm-1; λmax2 = 640 nm, ε = 120.0 M-1 cm-1. λmax3 = 576 nm, ε = 71.2 M-1 cm-1.

3. Crystallographic analysis of {CoV4}

Suitable single crystals of 1 were grown and mounted using a MicroLoop and Fomblin

oil. X-ray diffraction intensity data were measured at 150 K on a Nonius Kappa CCD

diffractometer [λ(Mo-Kα) = 0.71073 Å] equipped with a graphite monochromator.

Structure solution and refinement was carried out using the SHELX-97 packageS2 via

WinGX.S3 Corrections for incident and diffracted beam absorption effects were applied

using empirical methods.S4 Structures were solved by a combination of direct methods

and difference Fourier syntheses and refined against F2 by the full-matrix least-squares

technique. Crystallographic data and structure refinements for compound 1:

C50H111Co1N3O14V4, Mr = 1241.11 g mol–1; block crystal: 0.18 × 0.15 × 0.13 mm3; T =

150(2) K. Monoclinic, space group P21, a = 11.8530(7), b = 21.6446(12), c =

12.5652(11) Å, β = 93.647(6), V = 3217.1(4) Å3, Z = 2, ρ = 1.281 g cm–3, µ(MoKα) = 0.868

mm–1, F(000) = 1326, 89091 reflections measured, 14733 unique (Rint = 0.0390), 659

refined parameters, R1 = 0.0455, wR2 = 0.1140. CSD 834843 contains the

supplementary crystallographic data. These data can be obtained free of charge via

www.ccdc.cam.ac.uk/conts/retrieving.html or deposit@ccdc.cam.ac.uk.

A suitable crystal of compound 2 was selected and mounted using a MicroLoop and

Fomblin oil on a SuperNova, Dual, Cu at zero, Atlas diffractometer. The crystal was kept

at 180.00(14) K during data collection. Using Olex2S5, the structure was solved with the

ShelXS structure solution program using Direct Methods and refined with the ShelXLS2

refinement package using Least Squares minimization. Crystallographic data and

structure refinements for compound 2: C55H113CoN3O14V4 (M =1303.17): monoclinic,

space group Cc (no. 9), a = 24.1500(4) Å, b = 23.6855(4) Å, c = 23.9678(4) Å, β =

93.9267(14)°, V = 13677.5(4) Å3, Z = 8, T = 180.00(14) K, µ(MoKα) = 0.820 mm-1,

Dcalc = 1.266 g/mm3, 54985 reflections measured (6.16 ≤ 2Θ ≤ 65.598), 31955 unique

(Rint = 0.0279, Rsigma = 0.0466) which were used in all calculations. The final R1 was

0.0436 (I > 2σ(I)) and wR2 was 0.1036 (all data).

Table S1. Crystal data and structure refinement compounds 1 and 2

Compound 1 Compound 2

Identification code CCDC 834843 CCDC 1001987 Empirical formula C50H111CoN3O14V4 C55H113CoN3O14V4 Formula weight 1241.11 1303.17 Temperature/K 150(2) 180.00(14) Crystal system monoclinic monoclinic Space group P21 Cc a/Å 11.8530(7) 24.1500(4) b/Å 21.6446(12) 23.6855(4) c/Å 12.5652(11) 23.9678(4) α/° 90.00 90 β/° 93.647(6) 93.9267(14) γ/° 90.00 90 Volume/Å3 3217.1(4) 13677.5(4) Z 2 8 ρcalcmg/mm3 1.281 1.266 m/mm-1 0.868 0.820 F(000) 1326.0 5560.0 Crystal size/mm3 0.25 × 0.18 × 0.16 0.2379 × 0.1958 × 0.1528 Radiation MoKα (λ = 0.71073) MoKα (λ = 0.71073) 2Θ range for data collection 6.62 to 55° 6.16 to 65.598°

Index ranges -15 ≤ h ≤ 15, -28 ≤ k ≤ 28, -16 ≤ l ≤ 16

-36 ≤ h ≤ 36, -35 ≤ k ≤ 35, -32 ≤ l ≤ 34

Reflections collected 89091 54985

Independent reflections 14733 [Rint = 0.0390, Rsigma = 0.0330]

31955 [Rint = 0.0279, Rsigma = 0.0466]

Data/restraints/parameters 14733/1/659 31955/3829/1414 Goodness-of-fit on F2 1.084 1.021 Final R indexes [I>=2σ (I)] R1 = 0.0455, wR2 = 0.1101 R1 = 0.0436, wR2 = 0.0926 Final R indexes [all data] R1 = 0.0539, wR2 = 0.1140 R1 = 0.0633, wR2 = 0.1036 Largest diff. peak/hole / e Å-3 0.93/-0.50 0.35/-0.35 Flack parameter 0.012(15) -0.018(5)

Figure S3: ORTEP representation of compound 1 (CCDC 834843), thermal ellipsoids given at 50 % probability.

Figure S4: ORTEP representation of compound 2 (CCDC 1001987), thermal ellipsoids given at 50 % probability.

Compound (n-Bu4N)3[CoV4O12Cl]S6 is registered under CCDC 721230.

4. NMR spectroscopy

Figure S5: 1H-NMR spectrum of {CoV 4} (left) and Co(AcO) 2×6H2O (right) in DMSO-d6. See Table S2 for peak assignment. The AcO- methyl signal is observed at δ = 1.92 for {CoV 4} and at δ = 2.51 for Co(AcO)2x6H2O. Table S2 : 1H-NMR peak assignment:

δ / ppm Peak # Peak assignment

No of H from integration

(referenced to the n-Bu 4N - CH3

group at 0.92ppm)

{CoV 4}

0.92 4 N-CH2-CH2-CH2-CH3 12.00

1.20 3 N-CH2-CH2-CH2-CH3 8.16

1.52 2 N-CH2-CH2-CH2-CH3 8.04

1.92 5 CH3-COO- 3.12

2.85 1 N-CH2-CH2-CH2-CH3 7.08

Co(AcO) 2×6H2O

2.09 3 CH3-COO-

2.51 2 DMSO-d6

3.38 1 H2O

5. ESI mass spectrometry

ESI mass spectrometry was performed in acetonitrile ([1] = 100 µM) in negative ion

mode.

Figure S6: Experimental and simulated isotopic pattern of 1 with the loss of one acetate ligand. (n-Bu4N)[CoV4O12]

– at m/z = 696.9328.

Figure S7: Experimental and simulated isotopic pattern of 1: CoII[CoII(AcO)V4O12]– at

m/z = 572.5946.

6. Thermogravimetric analysis

Figure S8: Thermogravimetric analysis of {CoV 4} showing one main mass loss step (exp: 64.1 wt.-%) between ca. 203 ˚C and ca. 500 ˚C, assigned to the loss of three n-Bu4N

+ counterions (calcd. 58.6 wt.-%) and one acetate group (4.8 wt.-%, in sum 63.4 wt.-%). This is in line with the formula assigned from single-crystal XRD.

7. UV-Vis studies

7.1. Molar extinction coefficient of {CoV 4}

The molar extinction coefficients for {CoV 4} were determined by dissolving {CoV 4} in

DMF solutions containing a large excess of acetate so as to drive the equilibrium fully to

the {CoV 4} side. The experiment was conducted at several initial {CoV 4} concentrations

and gave virtually identical molar extinction coefficients. Three d-d-transitions are

observed at λ1 = 576 nm (ε576 = 71.3 M-1 cm-1), λ2 = 640 nm (ε640 = 120.0 M-1 cm-1) and λ3

= 724 nm (ε724 = 242.7 M-1 cm-1). For monitoring spectral changes upon acetate addition,

the absorption signal a λ = 724 nm was used.

7.2 Co(NO3)2 / {V4} titration series – acetate addition

For acetate-dependent sensor response studies, solutions of Co(NO3)2 × 6H2O and {V4}

(molar ratio 1:1, [{V4}]= 5 mM) were titrated with DMF-solutions of n-BuN4(AcO) as

acetate source.

Figure S9: UV-Vis spectroscopic titration demonstrating the effect of acetate on the formation of {CoV 4} in solution. Various equivalents of acetate were added to solutions containing 1:1 molar ratios of [Co(NO3)2] / [{V4}].

Figure S10 : UV-Vis spectroscopic titration demonstrating the effect of acetate on the formation of {CoV 4} in solution. Various equivalents of acetate were added to solutions containing 1:1 molar ratios of [Co(NO3)2] / [{V4}].

The effects of the {V4} cluster on the spectral response to acetate-binding was studied

using the reaction between acetate and a DMF solution of Co(NO3)2 × 6H2O (5mM). The

results show that acetate-binding also results in increased absorbance, however, in

contrast to the {CoV 4} system, here, smaller changes in the molar extinction coefficients

are observed together with an overall less characteristic spectral response, compare Fig.

S8 and S9.

Figure S11 : UV-Vis spectroscopic titration showing the spectral changes observed by addition of n-Bu4N(AcO) to a DMF solution of Co(NO3)2 × 6H2O (5mM).

The spectral response to chloride-binding was studied using the reaction between chloride and a DMF solution of {V4} and Co(NO3)2 × 6H2O (1:1, 5mM each). The results show that distinct spectral changes and increased absorbance are observed, these signals can be distinguished from acetate binding, see above.

Figure S12 : UV-Vis spectroscopic titration showing the spectral changes observed by addition of n-Bu4NCl to a DMF solution containing 1:1 molar ratios of [Co(NO3)2] / [{V4}] (5 mM).

7.3. Ratiometric behaviour

Figure S13 : Linear ratiometric range of acetate detection showing the concentration of {CoV 4} in solution as a function of the acetate concentration. Linear range for acetate ca. 0.5 – 4 mM, [Co(NO3)2] = [{V4}]= 5 mM.

7.4 {CoV 4} – addition of acetate

Figure S14 : UV-Vis spectroscopic titration of acetate to a solution containing dissolved crystals of {CoV 4} ([{CoV 4}] = 10 mM in DMF). The data shows that upon dissolution, an equilibrium is obtained between {CoV 4} and non-cluster bound CoII / {V4} / AcO-, see Scheme S1. Acetate addition shifts this equilibrium to the {CoV 4} side, thus higher {CoV 4} signal intensities are observed.

7.5 Solution equilibrium upon dissolving {CoV 4} in DMF

Figure S15 : [{CoV 4}] observed in solution (solvent: DMF) as a function of the amount of {CoV 4} dissolved. The dissociation constant Kd was calculated based on the following equation: Kd = [CoV4O12

4-] x [AcO-] / [Co(AcO)V4O123-]

Equilibrium concentrations of the three components were determined photometrically using the known extinction coefficients. kd

60% = 2.78 × 10–1 mM kd

95% = 3.23 × 10–2 mM 7.6. Anion-selective spectral response of {CoV 4} To investigate the anion-dependent behavior of {CoV 4}, DMF-solutions containing {V4} (5 mM), Co(NO3)2 × 6H2O (5 mM) and n-Bu4NX (x = PF6

-, PhCOO-, Cl-, [X] = 0.5 - 25 mM) were prepared and the spectral response to the anion was measured. As shown below, distinct spectral responses were observed for each anion, so that anion-selective detection becomes possible.

Figure S16 : Spectral response of a 1:1 molar mixture of {V4} and Co(NO3)2 × 6H2O upon addition of 5 equivalents of the corresponding n-Bu4N(X) salt (X = PF6

-, PhCOO-, Cl-), [X] = 25 mM. Solvent: DMF.

Figure S17 : UV-Vis spectra of 5 mM solution of the educts and corresponding {CoV4} solution in DMF. n-Bu4N(X) salts and {V4} are not absorbing light at the given wavelength-area.

7.7. Thermal stability evaluation of {CoV 4} The thermal stability of {CoV4} was evaluated by heating a sample of {CoV4} dissolved in DMF for 24 h to T = 90 oC. UV-Vis spectra were recorded before and after the heat treatment and virtually no changes to the characteristic UV-Vis signals of {CoV 4} can be observed, see below.

Figure S18: UV-Vis spectroscopic analysis of solution of {CoV4} in DMF before (red line) and after (black line) heating the sample to T = 90 oC for 24 h.

8. Literature references cited in ESI

S1 J. Forster, J.; Rösner, B.; Khusniyarov, M. M.; Streb, C.; Chem. Commun., 2011,

47, 3114.

S2 Sheldrick, G.M.; Acta Crystallogr. 2008, A64, 112.

S3 Farrugia, L. J.; J. Appl. Cryst. 1999, 32, 837.

S4 Blessing, R. H.; Acta Crystallogr. 1995, A51, 33.

S5 Dolomanov, O.V., Bourhis, L.J., Gildea, R.J, Howard, J.A.K. & Puschmann, H., J. Appl. Cryst. 42, 2009, 339-341

S6 Kurata, T.; Hayashi, Y.; Isobe, K.; Chem. Lett. 2009, 38, 218–219.